What are bezoars and can they really treat poisoning?

In the opening Harry Potter novel, Professor Severus Snape tries to humiliate Harry by testing his knowledge of bezoars. Snape describes these as hard masses found in a goat's stomach that can counteract most poisons. Bezoars later save Ron Weasley after he is poisoned.

The term bezoar has roots in Persian and Arabic, where it means "antidote" and "against poisons" – probably the source of J.K. Rowling's inspiration. Yet many Harry Potter fans may not know that bezoars are not simply an invention from Rowling's fictional world.

Although they can occur in the stomachs of goats and other animals, people can also form bezoars. This is uncommon, but they may develop in the stomach, intestines, gullet and even the windpipe.

Their size and weight vary considerably. In July 2024, surgeons removed a 41cm mass of hair, weighing 0.9kg, from the stomach of a 24-year-old woman in Manabi, Ecuador. In March 2024, doctors in Newcastle extracted a 15cm hairball from a seven-year-old girl's stomach. Reports stated that it occupied 80 percent of her bowel.

Bezoars often look stony and may consist of any substance that cannot be digested or absorbed through the intestinal wall. The material therefore builds up within the lumen – the gut's hollow interior – and steadily grows larger.

A person generally needs particular circumstances to form a bezoar: consuming indigestible matter alongside a sluggish digestive system. This prevents the material from passing through the gut and leaving the body as faeces.

Types of bezoar

There are many forms of bezoar, normally categorised by their contents. Phytobezoars, for instance, are made from plant matter. Plants contain large amounts of cellulose, a compound that humans cannot digest.

Eating persimmons can, however, lead to diospyrobezoars, a type of phytobezoar linked specifically to excessive intake of this fruit. Persimmons contain particularly high levels of tannins, which produce their bitter taste, especially before ripening. These tannins have been recognised as posing a high risk of bezoar formation.

Numerous other substances may form bezoars. Fibres from fruit and vegetables, milk, medicines and gums – including swallowed chewing gum – can create an indigestible mass in the stomach. Ingesting inorganic materials, such as paper, polystyrene and plastic, may also result in bezoars.

This is especially linked with pica, a condition involving cravings for inedible items or substances without nutritional value, and one most commonly seen in pregnant women.

Not every bezoar is hard and stony. Trichobezoars consist of swallowed hair, which can collect in the body in the same way that a cat develops a hairball. Over years of hair swallowing, this may cause Rapunzel syndrome, named for the fairytale heroine, in which the bezoar becomes progressively larger and longer.

For some patients, surgery is needed to remove a substantial mass of hair from the bowel, said to look like Rapunzel's lengthy plait.

Bezoars through the ages

Hard bezoars taken from animals were once sought-after collectors' objects, largely because people believed they could cure poisoning.

They probably existed as collectables in the Middle East well before reaching medieval Europe. During the era of kings, lords and merchants, when many feared assassination by poison, people would place a bezoar in their drinking vessel as a supposed safeguard. In reality, it would have had zero success.

Even so, bezoars remained valued curiosities. Some were turned into jewellery, while others were embellished with gold and gemstones for private collections. They are still exhibited by certain medical museums, including London's recently refurbished Hunterian Museum.

Modern-day bezoars

As with other hard bodily masses, including gallstones and renal calculi, bezoars may cause no symptoms unless they move into narrower areas and become lodged there. They can consequently remain undetected for years.

When they do create symptoms – including nausea, abdominal pain and vomiting, or even gastric ulcers and bleeding – several removal options are available. A sufficiently small bezoar can be taken out with an endoscope, an instrument with a camera that allows clinicians to look inside the gut and extract the stone. Larger bezoars may need surgical removal.

One non-invasive approach for certain bezoars, including persimmon stones, involves dissolving them using salt solutions, enzyme preparations and, unexpectedly, cola.

However, medical opinion remains divided over how effective this method of dissolving bezoars is. More concerningly, if these treatments might dissolve a stone, what else could they be doing to the stomach?

If you are susceptible to bezoars or concerned about developing one, avoid higher-risk foods including persimmons, celery, pumpkin, prunes and sunflower seed shells. Chew food carefully before swallowing, do not swallow indigestible non-food items such as hair, and seek medical advice if pica is a concern.

Dan Baumgardt, Senior Lecturer, School of Physiology, Pharmacology and Neuroscience, University of Bristol

This article is republished from The Conversation under a Creative Commons licence. Read the original article.